Preparation of diphenylphosphinous azide and polymers derived therefrom



United States Patent 2 Claims. (Cl. 260-561) The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This is a division of application Serial No. 318,767, filed October 24, 1963, now U.-S. Patent 3,211,753.

The present invention relates to elastomers and more particularly to a method tor the synthesis of diphenylphosphinous azide of the formula (C H PN to be used subsequently in the preparation of thermally stable phosphonitrilic polymers which are useful as lubricants, sealing agents, and elastomers having improved stability and thermal characteristics.

Diphenal phosphinous azide, as prepared by the method disclosed herein, can be reacted with chain terminating agents; i.e., trivalent phosphorus derivatives thus avoiding ring formation and resulting in linear polymers.

Diperfiuoromethylphosphinous azide (OF P|N was synthesized by C. M. Douglas, G. Tesi and C. P. Haber, as disclosed in US. Patent No. 3,087,937; however, their procedure used for the synthesis of (CF PN could not be applied to (C H FN since the latter decomposes with the formation ofmainly cyclic products under the conditions under which (CF PN was isolated.

It is an object of the invention .to provide a method for the synthesis of (CgH PN Another object of the invention is to provide an improved elastomer having improved stability and thermal characteristics, and a method of producing same.

It is also an object of the invention to provide preparation of linear chains by reacting diphenylphosphinous azide with phosphine derivatives.

A further object of the invention is to provide the synthesis of an intermediate for use in the preparation of thermally stable phosphonitrilic polymers.

Other objects and many of the attendant advantages of this invention will become readily appreciated as the same becomes better understood by reference to the following detailed description.

A procedure for the synthesis of diphenylphosphinous azide (C H )gPN is disclosed in Example I, as follows,

Example I The apparatus employed consisted of a ISO-ml. flask equipped with a horizontal sidearm with a sealed-in sintered glass disc, and a ground joint which permitted the attachment of another similar flask.

In the first flask 1.24 g. of finely powdered lithium azide was suspended in 25 ml. of acetonitrile. To this vigorously stirred mixture was added diphenylphosphinous chloride (1.229 g.) in acetonitrile (10 m1.) over a period ice of minutes. A mercury valve protected the system from the atmosphere. The stirring was continued for 7 hours at 18 to 14" C., during which period no pressure change could be observed. An aliquot withdrawn at that time was examined by infrared spectroscopy, a-

strong absorption at 4.78;; indicated the presence of an azide group attached to trivalent phosphorus. After the connection to the mercury valve was sealed, the system was attached to the vacuum line and acetonitrile was removed completely at 18 C. n-pentane ml. was dis tilled onto the residue at l96 C., the system was subsequently warmed to 20 C. for 1 hour, .and the solution filtered into the second ISO-ml. flask. There the product diphenylphosphin-ous azide (C HQ PIN was crystallized from the solution by cooling to 78 C. and the mother liquor was filtered olf. A portion of this solid was dissolved in n-butane and its molecular weight was determined by vapor pressure lowering technique.

Found: 276 Calcd.: for (C H PN 227 Another portion of this solid was warmed slowly from -=l5f C. in a clear sight Dewar cflask; at 13.5-13.8 C. It discolored deep yellow with simultaneous nitrogen evolution (identified by mass spectrometry). Subsequently the flask was heated for 2 hours at C. to drive the decomposition to completion. Amount of phosphorus in the decomposed sample0.572 mole. Amount Amount of nitrogen given elf-0.625 mole.

fiuorinated analogues, hydrogen or halogen. The particular preparation described below in Example II, concerns the formation of Using the same apparatus and procedure as described in Example I, diphenylphosphinous chloride (1.843 g.) was reacted with lithium azide (0.6 g.) in acetonitrile at ca. 20 to 25 C. The acetonitrile solution containing now (C H P*N was filtered under nitrogen atmosphere onto a solution of triphenylphosphine (3.2 g.) in acetonitrile (40 ml.) also at -25 C. The resulting solution was put into an ice bath, connected to a mercury valve and stirred vigorously. A rapid gas evolution was observed. The temperature of the solution was allowed to raise slowly to room temperature. No precipitate was observed on completion of the reaction.

Acetonitrile was removed by evaporation on the vacuum line and the product was separated from unreacted 3 triphenylphosphine' by sublimation, and by boiling with ligroine. The ligroine insoluble residue M.P. 57-61 C. was [(C6H5)2PN]3'P(C5H5)3.

Analysis.Calcd. ['(C H )PN] 'P(C H C, 75.43; H, 5.29; P, 14.40; N, 4.89; mol. Wet 860. Found: C, 74.0; H, 5.42; P, 14.08; N, 4.90; mol. wt. 785.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1'. The synthesis of comprising reacting in an inert atmosphere diphenylphosphinous chloride with lithium azide -in acetonitrile at a 20 to 25 (2., filtering the resulting mixture onto a from unreacted triphenylphosphine.

2. The compound [(C H PN] P(C H No references cited.

WALTER A. MODANCE, Primary Examiner. HARRY I. MOATZ, Assistant Examiner. 

1. THE SYNTHESIS OF 